Slurry suitable for high-pressure jet grouting pile construction in aeolian sand stratum

Abstract

The invention belongs to the technical field of rotary jet grouting of geotechnical engineering, and discloses slurry suitable for high-pressure rotary jet grouting pile construction in an aeolian sand stratum. The slurry material comprises the following components in parts by mass: 100 parts of silicate cement paste, 0.5-6 parts of water glass and 0.5-5 parts of a suspending agent. The effect of modifying ordinary cement slurry is achieved through reasonable additives and scientific proportioning, and the problems that the ordinary cement slurry is long in setting time, prone to precipitation and water separation, slow in strength increase, poor in pile forming type, broken and empty in high-pressure jet grouting pile construction in an aeolian sand layer are solved; and the method is suitable for construction in northern severe cold areas under proper environment conditions. The construction efficiency of the high-pressure jet grouting pile in the sandstorm stratum is improved, the economic cost of construction is saved, and the requirements for on-site rapid construction and quality are met.

Description

Technical Field

[0001] This invention relates to the field of jet grouting technology in geotechnical engineering, specifically to a grouting material suitable for high-pressure jet grouting pile construction in aeolian sandy strata. Background Technology

[0002] Due to its low cohesion, low shear strength, and fine particle size, aeolian sand is easily loosened and displaced under external forces, resulting in extremely poor surrounding rock stability. Therefore, during tunnel construction in aeolian sand formations, the weak self-stabilizing ability of the sand particles poses a significant risk of runoff, collapse, and even roof fall at the tunnel face if pre-reinforcement is not implemented. Consequently, research into key construction technologies for tunnels traversing aeolian sand formations is becoming increasingly urgent and important.

[0003] Traditional jet grouting construction uses ordinary silicate cement grout, a single-component grout, which has been widely used in soft soil foundation reinforcement, dam foundation seepage prevention curtains, dam and bridge foundation reinforcement, temporary support for buildings and structures, and soil improvement. However, ordinary cement grout has the following limitations in its application to aeolian sand layers: ① Long initial setting time. To meet the requirements of high-flow pumping, ordinary cement with an initial setting time of about 10 hours is commonly used. Due to the long setting time, the grout discharge flow at the borehole may be large during jet grouting, especially during the construction of horizontal jet grouting piles. This may result in the pile diameter failing to meet the design requirements, and the large amount of grout discharged will cause material waste and increase economic costs.

[0004] ② Due to the long final setting time and poor grout stability, the loss of grout in the stratum can easily form irregularly shaped piles such as "gourd piles" and "radish piles", which affects the interlocking between piles.

[0005] ③ Ordinary silicate cement is a suspension, which can easily cause uneven mixing. If left to stand for a long time, it will precipitate and release water. After solidification, the stone rate is low and the stability is poor, which may lead to quality problems such as broken piles and empty piles.

[0006] ④ Slow strength growth: Ordinary cement grout has a slow strength growth rate. After the jet grouting pile construction is completed, it takes a period of equal strength to meet the requirements of excavation construction, which affects the construction period.

[0007] ⑤ Environmental adaptability: In the frigid northern regions, ordinary cement grout has a high water content and cannot solidify in time. It may be affected by the environment and is prone to freezing and cracking, which can damage the strength of the pile and cause serious consequences.

[0008] In summary, ordinary silicate cement grout is economical and easy to apply, but grouting in aeolian sandy strata has problems such as long setting time, easy sedimentation and water separation, slow strength growth, and poor environmental adaptability in cold northern regions. These issues lead to reduced efficiency of high-pressure jet grouting and easy loss of grout, resulting in waste and affecting construction quality. Summary of the Invention

[0009] The purpose of this invention is to provide a grout material suitable for high-pressure jet grouting pile construction in aeolian sandy strata.

[0010] A grouting material suitable for high-pressure jet grouting pile construction in aeolian sandy strata comprises the following components by weight: 100 parts silicate cement slurry, 0.5-6 parts water glass, and 0.5-5 parts suspending agent.

[0011] The water-cement ratio of the silicate cement slurry is 0.5~2:1, preferably 0.5~1.2:1, and more preferably 1:1.

[0012] The suspending agent is at least one of magnesium aluminum silicate and bentonite.

[0013] Preferably, the slurry comprises the following components by weight: 100 parts silicate cement slurry, 1-4 parts water glass, and 1-2 parts suspending agent.

[0014] Most preferably, the slurry comprises the following components by weight: 100 parts silicate cement slurry, 3 parts water glass, and 1.4 parts suspending agent.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects: This invention achieves the effect of modifying ordinary cement grout through reasonable admixtures and scientific proportions, solving the problems exhibited by ordinary cement grout in high-pressure jet grouting pile construction in aeolian sand layers, such as long setting time, easy sedimentation and water separation, slow strength gain, poor pile shape, and broken or empty piles. It is also suitable for construction under suitable environmental conditions in cold northern regions. This improves the construction efficiency of high-pressure jet grouting piles in aeolian sand layers, saves economic costs, and meets the requirements for rapid on-site construction and quality. Adding 3% quick-setting agent (water glass) significantly shortens the initial and final setting times, reduces grout loss and waste, and improves grouting efficiency. Adding 1.4% suspending agent significantly improves the dispersibility of the cement grout, thereby minimizing grout settling and pipe blockage, and also increasing the compressive strength of the consolidated body. Attached Figure Description

[0016] Figure 1 From left to right, the graphs show the stability test results of pure water and the pulp materials in experimental groups 1-4 of Example 1. Figure 2 The graphs show the stability test results of the slurry in experimental groups 5-8 of Example 1. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. Unless otherwise specified, the reagents used in the embodiments can be obtained commercially available. The performance testing methods in the embodiments are shown below.

[0018] ①Setting time test At a given temperature, the time elapsed from the mixing of all the reacting components until the slurry loses its fluidity is called the gel time. The gel time can be further divided into initial setting time and final setting time. The initial setting time is the period from when the slurry is mixed until it begins to lose its fluidity; the final setting time is the period from when the slurry is mixed until it completely loses its plasticity and begins to develop strength.

[0019] According to the method in GB / T1346-2001 "Test Methods for Standard Consistency Water Requirement, Setting Time and Soundness of Cement", the setting time of the grout is tested using a Vicat apparatus. Figure 2 As shown: ② Flowability and pumpability time test The fluidity was measured using a cement paste flow test mold, and the average of the maximum and minimum diameters of the measured flow range was taken as the fluidity at that time point.

[0020] The pumpable time refers to the period from the completion of slurry preparation until the slurry fluidity is below 140 mm. The measurement of fluidity can be stopped when the slurry fluidity is 140 mm or below.

[0021] ③Water separation rate test After the prepared slurry has been left to stand for a period of time, varying degrees of water separation are observed. This indicates that after the slurry settles and gels, excess free water will precipitate out, which is generally characterized by the water separation rate. The water separation rate of the slurry over a certain period of time reflects the stability of the slurry and is one of the important parameters affecting the performance of the slurry. After the slurry is prepared, 250 ml of slurry is taken using a graduated cylinder with a measuring range of 250 ml. After the graduated cylinder is left to stand until the level of the precipitated water stabilizes, the volume of precipitated water in the graduated cylinder is read. The percentage of the precipitated water volume to the total volume of the slurry is the water separation rate of the slurry.

[0022] ④ Viscosity of the slurry Viscosity testing was performed using a ZNN-D6 six-speed rotational viscometer. The prepared slurry was stirred thoroughly and poured into a measuring cup, leveling the slurry with the graduation mark. The viscometer speed was then adjusted to 600, 300, 200, and 100 r / min. After the reading stabilized, the data was recorded, representing the shear stress at that speed. The test was conducted according to the required proportions to obtain the corresponding shear rate-shear stress parameters.

[0023] ⑤ Slurry stability test During high-pressure jet grouting pile construction, poor cement slurry stability can lead to free liquid and particle settling, easily clogging small guide pipes and causing quality defects such as broken piles and empty piles after jet grouting. To address this issue, in addition to adding water glass to improve the slurry gelation time, a copolymer cement suspending agent was developed to enhance slurry stability, making the silicate cement slurry less prone to stratification and settling. The suspending agent effect was tested by taking 250ml of the prepared slurry using a 250ml graduated cylinder, allowing the cylinder to stand for 2 hours until the upper suspension stabilized, and then comparing the volume of the suspension in the graduated cylinder to determine the suspending agent effect.

[0024] ⑥ Compressive strength test For cement-based suspensions, strength tests can be performed using solidified specimens of pure slurry; however, this test is a uniaxial compressive strength test.

[0025] The experiment used a YAS-300 microcomputer-controlled hydraulic servo pressure testing machine. Cement slurry, after reaching the pumpable stage, was poured into five identical 70.7×70.7×70.7 mm... 3 The cement slurry was placed in a standard triplet mold and then cured in a standard curing chamber at a temperature of 20°C and a relative humidity of over 90%. The compressive strength of the cement slurry aggregate was tested at curing ages of 7 days, 14 days, and 28 days. The average value of the compressive strength test results of the five sets of molds was taken as the compressive strength of the cement slurry aggregate of this mix. Example

[0026] To improve the stability of cement slurry, reduce cement particle settling, and avoid pipe blockage during grouting, a copolymer cement suspending agent was developed to enhance the stability of the cement slurry and prevent particle settling. Eight groups of suspending agent tests were conducted. PO42.5 grade ordinary Portland cement was used as the main material to prepare the cement slurry. Appropriate admixtures were added to improve the slurry's performance, and its basic properties were determined through the following tests: (1) Prepare silicate cement slurry, water glass and suspending agent in different proportions according to Table 1; (2) Add the raw materials from step (1) in the order of water, magnesium aluminum silicate suspension, cement and water glass, stir for 5 minutes and then let stand.

[0027] Table 1. Comparison of experiments with different contents of suspension concentrate

[0028] The properties of cement slurries with different contents of suspending agent are shown in Table 2.

[0029] Table 2. Test results of basic properties of cement slurry with different suspension concentrate contents

[0030] Comparative Example 1 Five groups of ordinary silicate pure cement slurries with water-cement ratios of 0.5, 0.7, 0.8, 1.0, and 1.2 were prepared. The performance of the pure cement slurries, including density, fluidity, pumpable time, water separation rate, viscosity, initial setting time, and final setting time, was tested. The raw materials and preparation steps of the cement slurries are as described in Example 1. The test results are shown in Table 3.

[0031] Table 3. Test results of basic properties of pure cement slurry

[0032] The results of the strength test are shown in Table 4.

[0033] Table 4 Compressive strength of pure cement paste with different water-cement ratios

[0034] The test results show that water-cement ratios of 0.5:1 and 0.7:1 have lower water separation rates, faster strength rise, and higher strength, but also lower grout fluidity, higher viscosity, and shorter initial setting time, which negatively impacts the efficiency of jet grouting pile construction. A water-cement ratio of 1.2:1 results in lower strength. Considering the performance and economics of the five grout ratios, and referencing engineering experience, a water-cement ratio of 1:1 for ordinary cement grout is the most reasonable and meets the technical requirements of high-pressure jet grouting pile construction. However, for aeolian sand layers, due to the special nature of the project and the time constraints, further modification of the grout is necessary to both meet the requirements of jet grouting pile construction and improve construction efficiency to meet the project schedule.

[0035] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that no suspending agent is added. The different amounts of water glass added and their performance are shown in Table 5.

[0036] Table 5. Effects of Different Water Glass Addition Amounts on Performance

[0037] Note: The amount of water glass used refers to its percentage by mass of cement.

Claims

1. A grouting material suitable for high-pressure jet grouting pile construction in aeolian sandy strata, characterized in that... Includes the following mass fractions: 100 parts silicate cement slurry, 0.5-6 parts water glass, and 0.5-5 parts suspending agent.

2. The slurry material according to claim 1, characterized in that... Includes the following mass fractions: The slurry comprises the following components by weight: 100 parts silicate cement slurry, 1-4 parts water glass, and 1-2 parts suspending agent.

3. The pulp material according to claim 1, characterized in that... Includes the following mass fractions: 100 parts silicate cement slurry, 3 parts water glass, and 1.4 parts suspending agent.

4. The pulp material according to any one of claims 1 to 3, characterized in that: The water-cement ratio of the silicate cement slurry is 0.5~2:

1.

5. The pulp material according to any one of claims 1 to 3, characterized in that: The suspending agent is at least one of magnesium aluminum silicate and bentonite.

6. The pulp material according to any one of claims 1 to 3, characterized in that: The water-cement ratio of the silicate cement slurry is 0.5~1.2:

1.

7. The pulp material according to any one of claims 1 to 3, characterized in that: The water-cement ratio of the silicate cement slurry is 1:1.

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